The invention relates to a saw band of steel for a rotary band saw machine according to the claims. The invention furthermore relates to a method for the production of a saw band.
Publication WO 2005/014877 A1 discloses the coating of a steel band in a roll-to -roll process, wherein on the band, preferably produced of cold-worked steel, a layer of different hard materials is applied on one side or, in successive process steps, on both sides. From this band subsequently a saw band can be produced.
Of disadvantage herein is that the coating takes place from the side. Therewith onto the functional faces (clearance area and chip area) exposed most strongly to wear the least layer thickness is applied and onto the less stressed side faces the greatest layer thickness, and consequently the costly coating material is poorly utilized. In addition, the coating is frequently applied on cold-worked steels which are only subsequently hardened, which can have a disadvantageous effect on the layer/substrate bond. On the other hand, such cold worked steels cannot be readily coated after the hardening, since conventional
PVD processes, i.e., physical vapor deposition processes, far exceed the tempering temperature of such materials. Low-temperature PVD processes, on the other hand, have the disadvantage of generating poorly adhering layers which, especially under high loading, such as during sawing and abrasive wear, is of significant disadvantage. Since the layer thicknesses known in prior art are significantly greater than 5 μm, they are expensive in production and do not offer any significant improvement compared to uncoated saws, since here the layer tends to break off at the saw point during the entering and, consequently, the advantages of the coating no longer come to bear here.
WO 2006/089753 discloses a steel saw band for a band saw machine which is provided with a hard material coating whose thickness on the clearance areas of the tooth row is greater than on the side faces. With such coated bands, excellent results could to some extent be achieved in long-term saw trials. However, it was found that these results were frequently not reproducible and, to some extent, layer spalling occurs already during the cutting-in process necessitating therefore a careful cutting-in process.
As already stated, in saw bands of prior art, which are conventionally produced by mill-cutting or grinding, a cutting-in process is necessary in which the band is operated at lower pressure and/or slower infeed. On the one hand, this is cumbersome and, on the other hand, lowers the productivity. If the cutting-in process is omitted, a strong rise of wear occurs at the teeth, at least in uncoated saw bands, and an increase of the cutting time with the band most often becoming unusable within a few cuts. In coated bands an increase of the cutting time can also be found which, as a function of the clearance angle α, differs in magnitude. Further, premature wear may occur which can have a negative effect inter alia due to the saw running untrue i.e. deviating from the predetermined cutting plane.